The invention pertains to rotatable element ball valves and more particularly to a construction of a ball valve having a removable strainer element and suitable for use in an aviation fuel delivery system.
Strainer ball valves are commonly used in aviation fuel delivery systems. In such systems a pump delivers fuel from a supply reservoir, such as an underground storage tank or tanker truck, through a delivery hose to a nozzle which is configured to mate with a fueling flange on an aircraft. Typically, a ball valve is located between the delivery hose and the nozzle and carries a strainer to prevent large particles of debris from entering the aircraft. Typical of such ball valves is the WL 3510 Strainer Ball Valve sold by WARNER LEWIS. That valve, has inlet and outlet ports located at opposite ends of a ball housing. The inlet port is configured for attachment to a delivery hose and the outlet port is configured for attachment to a fuel nozzle. A ball for controlling fuel flow is located intermediate the ports and is held for rotation about an axis perpendicular to the inlet and outlet ports. There is a flow passage formed through the ball and a strainer basket is mounted in the ball across the flow passage. The strainer basket has a mouth and a body. A keyed handle may be fitted into a slot in the ball through an opening in the housing aligned with the ball's axis of rotation.
The handle may be used to rotate the ball into one of three desired orientations. In a refueling orientation, the passage is located to allow communication between the inlet and outlet ports and the strainer mouth is positioned adjacent the inlet port such that debris will be strained from the fuel as it passes from the hose to the nozzle before entering the aircraft.
In a defueling orientation, wherein fuel is to be removed from an aircraft, the ball is rotated 180.degree. from the fueling orientation so that the mouth of the strainer is adjacent the outlet port. In this orientation, fuel is drawn from the aircraft through the nozzle, the outlet port, the strainer, the inlet port and then into the hose on its way back to the supply reservoir. In this orientation the strainer serves to prevent debris in the aircraft's fuel tanks from entering the supply reservoir.
In a third orientation, the flow passage is perpendicular to the inlet and outlet ports so that no communication is permitted therebetween. In this so called service orientation, the mouth of the strainer is adjacent a service port in the housing which is located perpendicular to the inlet and outlet ports. A cover is provided for the service port, which when removed allows inspection of the strainer as well as removal of the strainer for cleaning. A slot is provided in the cover so that a mating keyed handle may be used to unscrew the cover from the housing.
In the WARNER LEWIS ball valve, to remove the strainer, a worker must insert the keyed handle into the slot in the ball, rotate the ball to the service orientation, remove the handle, fit the handle into the service port cover, unscrew the service port cover and then extract the strainer from the ball and housing using a special tool.